Graduate Exam Abstract
January 9, 2018, 9:30 am - 11:30 am
Simultaneous Wireless Information and Power Transfer (SWIPT) in Cooperative Networks
Abstract: In recent years, the capacity and charging speed of batteries have become the bottleneck of mobile communications
systems. Energy harvesting (EH) is regarded as a promising technology to significantly extend the lifetime of battery-
powered devices. Among many EH technologies, simultaneous wireless information and power transfer (SWIPT)
proposes to harvest part of the energy carried by the wireless communication signals. In particular, SWIPT has been
successfully applied to energy-constrained relays that are mainly or exclusively powered by the energy harvested from
the received signals. These relays are known as EH relays, which attract significant attention in both the academia and
In this research, we investigate the performance of SWIPT-based EH cooperative networks and the optimization
problems therein. Due to hardware limitations, the energy harvesting circuit cannot decode the signal directly. Power
splitting (PS) is a popular and effective solution to this problem. Therefore, we focus on PS based SWIPT in this
In the first part of this research, we investigate the application of SWIPT in full-duplex (FD) EH relay networks. Different
from existing work that employs time-switching (TS) based SWIPT, we propose to use PS based SWIPT. As a result,
our proposed approach gives rise to a truly FD EH relay network, where the information reception and transmission
take place simultaneously at the relay all the time. This more thorough exploitation of the FD feature consequently
leads to a significant capacity improvement compared with existing alternatives in the literature. Furthermore, we
explore the relay selection (RS) problem in FD EH relay networks. Both single relay selection (SRS) and general relay
selection (GRS) without the limit on the number of cooperating relays are investigated and the corresponding RS
methods are proposed. We will show that our proposed heuristic GRS methods outperform the SRS methods and
achieve very similar performance compared with the optimal RS method achieved by exhaustive search but with
dramatically reduced complexity.
In the second part of this research, we study the problem of power allocation and PS factor optimization for SWIPT over
doubly-selective wireless channels. In contrast to existing work in the literature, we take the channel variation in both
time and frequency domains into consideration and jointly optimize the power allocation and the PS factors. The
objective is to maximize the achievable data rate with constraints on the delivered energy in a time window. Since the
problem is difficult to solve directly due to its nonconvexity, we proposed a two-step approach, named joint power
allocation and splitting (JoPAS), to solve the problem along the time and frequency dimensions sequentially.
Simulations show significantly improved performance compared with the existing dynamic power splitting scheme. A
suboptimal heuristic algorithm, named decoupled power allocation and splitting (DePAS), is also proposed with
significantly reduced computational complexity and simulations demonstrate its near-optimum performance.
Adviser: Liuqing Yang
Non-ECE Member: Haonan Wang, Statistics
Member 3: Edwin Chong, ECE
Addional Members: Rockey Luo, ECE
 D. Wang, R. Zhang, X. Cheng, Z. Quan, and L. Yang, “Joint Power Allocation and Splitting (JoPAS) for SWIPT in Doubly Selective Vehicular Channels,” IEEE Trans. Green Commun. Netw., vol. 1, no. 4, pp. 494–502, Dec. 2017.
 D. Wang, R. Zhang, X. Cheng, L. Yang, and C. Chen, “Relay Selection in Full-Duplex Energy-Harvesting Two-Way Relay Networks,” IEEE Trans. Green Commun. Netw., vol. 1, no. 2, pp. 182–191, Jun. 2017.
 D. Wang, R. Zhang, X. Cheng, and L. Yang, “Capacity-Enhancing Full-Duplex Relay Networks based on Power-Splitting (PS-)SWIPT,” IEEE Trans. Veh. Technol., vol. 66, no. 6, pp. 5445–5450, Jun. 2017.
 D. Wang, R. Zhang, X. Cheng, and L. Yang, “Relay Selection in Two-Way Full-Duplex Energy-Harvesting Relay Networks,” in IEEE Global Communications Conference (GLOBECOM), pp. 1–6, Dec. 2016.
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 D. Wang, X. Cheng, and L. Yang, “Joint Power Allocation and Splitting (JoPAS) for SWIPT in Time-Variant Wireless Channels,” in IEEE Global Communications Conference (GLOBECOM), pp. 1–5, Dec. 2016.
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 D. Wang, Q. Wang, H. Cheng, and H. Huang, “An improved motion-search method based on pattern classification,” in IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), pp. 2134–2137, Mar. 2010.
Program of Study: